The major source of vitamin D is dermal biosynthesis catalyzed by ultraviolet B sunlight (Cashman et al, 2011). However, during winter, northern Sweden has limited hours of daylight leading to reduced sun exposure. Consequently, the dietary source of vitamin D is of specific importance in this region (Brustad et al, 2007, Edvardsen et al, 2007). Fatty fish, eggs, vitamin D fortified milk and margarines are the main sources, mainly supplying the most active form D3. These are important basic foods which also contain common food allergens. Thus, children with food allergies to milk, fish, and egg can be at increased risk of vitamin D deficiency. Several dairy products are fortified with vitamin D, but in some products in the form of D2 which is not as bioactive as D3.